1.概说在纵横制中我们知道,纵横机的每一个纵单位都相当于一个10线、20线或更多线的选择机键。我们习惯地用小园圈加一短划表示一个纵单位,同一纵横机的纵单位置于一长方形框内,这里园圈代表静簧,而短划则代表动簧。这种画法简单明了,井能看出其内部连接情观。图1画出其表示方法。图2示明一个纵横机的内部连接图。(a)图所 1. Introduction In aspect control we know that every vertical unit of a horizontal plane is equivalent to a 10-line, 20-line or more line selection key. We used to use a small circle plus a short stroke to indicate a vertical unit. The vertical unit of the same horizontal plane is placed in a rectangular frame, where the circle represents the spring, and the short stroke represents the moving spring. This method is simple and clear, well can see the internal connection situation. Figure 1 shows its representation. Figure 2 shows the internal connection of a crossbar machine. (a) Picture